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Pes hippocampi

The pes hippocampi is the rounded anterior extremity of the hippocampus, forming the head of the hippocampus within the medial temporal lobe. It is characterized by multiple small surface indentations that resemble the toes of an animal’s paw, giving rise to its name (“pes” meaning foot).

The pes hippocampi is an important anatomical landmark in medial temporal lobe anatomy and imaging, particularly in the assessment of hippocampal morphology, memory-related structures, and surgical planning.

Synonyms

  • Hippocampal head

  • Pes hippocampi of the hippocampus

Location

  • Located in the anteromedial temporal lobe

  • Forms the anterior end of the hippocampus

  • Situated along the floor of the temporal horn of the lateral ventricle

  • Posterior to the amygdala

  • Inferior and medial to the temporal neocortex

  • Continuous posteriorly with the body of the hippocampus

Anatomical features

  • Digitations:

    • Series of rounded ridges or “toes” on the surface

    • Represent folded hippocampal gray matter

  • Gray matter structure:

    • Composed primarily of cornu ammonis (CA) fields and dentate gyrus

  • Orientation:

    • Broader and more complex than the hippocampal body

    • Gradually tapers posteriorly

Relations

Superiorly:

  • Temporal horn of the lateral ventricle

Inferiorly:

  • Parahippocampal gyrus

Anteriorly:

  • Amygdala (separated by the uncal recess)

Posteriorly:

  • Body of the hippocampus

Medially:

  • Uncus

  • Ambient cistern

Laterally:

  • Temporal lobe white matter

Structures associated

  • Cornu ammonis (CA1–CA4)

  • Dentate gyrus

  • Subiculum (posteroinferior transition)

  • Fimbria (posterior continuation)

Function

  • Memory encoding: Plays a key role in the formation of new declarative memories

  • Spatial navigation: Contributes to spatial orientation and contextual mapping

  • Limbic integration: Participates in emotional and behavioral processing

  • Information relay: Acts as an interface between hippocampus and broader limbic circuitry

MRI appearance (normal)

T1-weighted images:

  • Pes hippocampi: Intermediate gray-matter signal

  • Digitations: Best appreciated on high-resolution coronal images

  • Clear separation from the amygdala anteriorly

T2-weighted images:

  • Normal: Intermediate signal intensity

  • Internal architecture: Smooth, well-defined contours

  • CSF contrast: Clear delineation from the temporal horn

FLAIR:

  • Normal: Homogeneous signal without focal abnormalities

Diffusion-weighted imaging (DWI):

  • Normal: No diffusion restriction

Post-contrast T1-weighted images:

  • Normal: No enhancement

CT appearance (normal)

Non-contrast CT:

  • Pes hippocampi: Typically not individually distinguished

  • Medial temporal lobe: Appears homogeneousn

Post-contrast CT:

  • Normal: No focal enhancement

MRI images

MRI Pes hippocampi axial anatomy image -img-00000-00000

MRI images

MRIPes hippocampi axial anatomy image -img-00000-00000